A cosmetic has various forms such as liquid, emulsion, gel, cream, stick, or the like. Various thickeners and gelators are used to improve the feeling of use and maintain properties of a product. Conventionally, examples of aqueous thickening and gelling agent for cosmetics may include water-soluble polymers including a natural polymer such as sodium hyaluronate, sodium alginate, and xanthan gum, a semisynthetic polymer such as hydroxyethyl cellulose and carboxymethyl cellulose, and a synthetic polymer such as a carboxyvinyl polymer, a polyvinyl alcohol, and polysodium acrylate. The thickening and gelling agent is appropriately selected from these and used depending on the purpose and the effect.
However, many thickening and gelling agents for cosmetics including a carboxyvinyl polymer that is mainly used are ionic. Therefore, the thickening and gelling agents have such problems that the viscosity of a cosmetic rapidly decreases due to an electrolyte such as sweats during application of the cosmetic to the skin, to slide down the cosmetic from the skin, and the cosmetic is unlikely to be applied due to the electrolyte. In order to solve such problems, an attempt to enhance the salt resistance and impart excellent feeling of use is made. For example, an aqueous gel cosmetic containing a carboxyvinyl polymer, a basic substance, a hydrophobic silicic anhydride, and a polyhydric alcohol (e.g., Patent Document 1) and the like have been proposed.
Further, in order to suppress stickiness during application, improve the feeling of use, and impart spray properties, an aqueous medium that is gelled by a low-molecular gelator is tried to be used as a cosmetic base material (Patent Document 2). The low-molecular gelator self-assembles to form a fiber form, resulting in a network structure, and the network structure encloses the aqueous medium and the like to form a gel. The gel is used for the cosmetic base material. Therefore, the gel can be immediately converted into a sol with adequate stress applied to the gel (cosmetic base material), to impart the spray properties to a cosmetic. Since the low-molecular gelator is not dissolved (molecules are not dispersed) in the aqueous medium, the feeling of use during application to the skin is improved. This is because an increase in viscosity of a solution and adherence when dried is suppressed to reduce stickiness and clumping.
Moreover, a gel cosmetic containing a low-crystalline regenerated cellulose obtained by a treatment with sulfuric acid, plant-derived oils, and a nonionic surfactant (Patent Document 3) has been proposed. Patent Document 3 describes that in order to achieve thixotropy in which the gel cosmetic can be sprayed in a mist form, cellulose fine particles having an average degree of polymerization of 100 or less, a fraction of cellulose I type crystal component of 0.1 or less, and a fraction of cellulose II type crystal component of 0.4 or less are preferred.
Using a cosmetic containing cellulose fibers obtained from plant-derived cellulose without a chemical treatment and a polyhydric alcohol, increased moisture retention and reduced stickiness are attempted (Patent Document 4).